223 



columella sliort, spiral : nacre none ; muscular impressions two, 

 lateral, distant; a slightly revolving, elevated line on the inner 

 surface; operculum none. 



Animal tongue-shaped, chiefly formed by a very long, and very 

 thick foot, which is narrower and massive before, truncated behind, 

 canalieulated on each side and widely margining on all sides the 

 contorted visceral mass, which is very small, slightly convex above, 

 and covered by an interior shell; head depressed; mouth very 

 small, concealed under the anterior and superior margin of the 

 foot; teutaeula two, compressed and appcndiculated at base; a 

 large branchial pecten ; male organ under the right tentaculum ; 

 mantle without emargination. 



Obs. That able anatomist, Blainville, was the first to detect the 

 difference between the animal of the much depressed species of 

 the genus Sigaretus, Adans., and of those with a more elevated 

 spire ; and notwithstanding the similarity of the shells he very 

 judiciously separated them and formed the present genus, if we 

 may judge by the characters he has stated, for which we rely en- 

 tirely on his accuracy. It differs much from Coriocella, Blainv., 

 the animal of which has a very small foot and a coriaceous shell. 



C. PERSPECTIOUS, S. 

 G. MACULOTUS, S. 



-In attempt to exhibit a Synonymy of the Western North American species of 



the genera Unto and Alasmodonta. 



UNIO. 



1. U. NIGER, Eafinesque.* 5. U. fragilis, R. Sw. Deshayes. 



cuneatus, Barnes. gracilis, B. Hildr. Lea. Eaton. 



2. U. CARiosus, S. Lam. B. ^- U- nervosus, R. 



viridis,niii. zigzag, -Lq^. 



siliquoides, B. (var.) donaaformis, Lea. 



radiatus ? Gm. ^_ U. l^evigatus, R. 



, „ „ . castaneus ? Lea. 



3. TJ. FASCiATUS, Raf. 



carinatus, B. 8. U. rectus, Lam. Valenc. Eaton. 



latissimus, R. 



4. U. LEPTODON, Raf. proelongus, B. Hildr. 



planus, B. 



purpurescens, Swainson. 9. U. dilatatds, R. 



tenuissimus, Lea. nasutus, Lam. 



gibbosus, B. Hildreth. 



* This writer and some others imitated Lamarck in giving the specific name in 

 this genus a feminine termination, which we have changed in this table. 



